Investigate view's mini pager inconsistency

Problem/Motivation

The behavior of mini pager seems inconsistent.

/admin/test-ce?_content_format=json&page=0 or without page query param

    "pager": {
      "totalPages": 2,
      "current": 0
    },

/admin/test-ce?_content_format=json&page=1

    "pager": {
      "totalPages": 3,
      "current": 1
    },

/admin/test-ce?_content_format=json&page=2

    "pager": {
      "totalPages": 4,
      "current": 2
    },

/admin/test-ce?_content_format=json&page=3 and /admin/test-ce?_content_format=json&page=4

    "pager": {
      "totalPages": 4,
      "current": 3
    },

page=5 ...

  "content": {
    "element": "drupal-view",
    "title": "CE page",
    "viewId": "lupus_decoupled_view",
    "displayId": "custom_elements_page",
    "pager": {
      "totalPages": 5,
      "current": 4
    },
    "rows": []
  },